Use of Organic Acids or a Salt Thereof in Surfactant-Based Enhanced Oil Recovery Formulations and Techniques

ABSTRACT

The present disclosure provides a surfactant formulation for use in treating and recovering fossil fluid from a subterranean formation. The surfactant formulation includes a nonionic surfactant, organic acid selected from citric acid, diglycolic acid, glycolic acid and a salt thereof and injection water. The surfactant formulation may be injected into one or more injection wells located within the subterranean formation and fossil fluids can then be subsequently recovered from one or more producing wells

FIELD OF THE INVENTION

The present disclosure is directed to surfactant formulation containinga nonionic surfactant, an organic acid selected from citric acid,diglycolic acid, glycolic acid and a salt thereof and injection waterand to a process for recovering fossil fluids from subterraneanreservoirs employing such surfactant formulations.

BACKGROUND INFORMATION

Fossil fluids are generally recovered from underground formations bypenetrating the formation with one or more wells and pumping orpermitting the fossil fluid to flow to the surface through the well. Inprimary recovery, a natural driving energy such as an underlying activewater drive or a gas under some minimum pressure may possess sufficientpressure to drive the fluid to the well and then to the surface. In manyinstances, the natural driving energy is insufficient or becomesinsufficient to cause the fluid to flow to the well. Thus, a substantialportion of the fossil fluid to be recovered can remain in the formationafter depletion of the natural driving energy. In such cases, varioussecondary or tertiary recovery techniques must be applied to recover theremaining fluid.

One such technique involves the injection of water through one or moreinjection wells to drive the residual fluid towards a producing well.When the injection of water no longer results in acceptable rates ofproduction, the producing well must either be abandoned or subjected toother processes to further increase extraction. A variety of processesare known including steam flooding, polymer flooding, alkali flooding,miscible flooding with carbon dioxide, and flooding with aqueoussurfactant solutions. With respect to flooding with an aqueoussurfactant solution, a surfactant package is added to the injectionwater and injected into the well for the purpose of decreasing theinterfacial tension between the injection water and fossil fluid phasesthus leading to an increase in fossil fluid extraction. The challengeone skilled in the art faces when implementing such a process isdetermining an effective combination of components which make up thesurfactant package. Many combinations must generally be tried before asuitable surfactant package can be formulated having good tolerancetowards the multivalent cations found in the brine of many formations aswell as having low adsorption onto rock of the formation. For example:

-   -   U.S. Pat. No. 3,811,504 discloses the use of a three surfactant        system containing an alkyl sulfate, an alkyl polyethoxylated        sulfate, and a polyethoxylated alkylphenol;    -   U.S. Pat. No. 3,890,239 discloses a surfactant composition        useful in recovering oil from a formation that includes an        organic sulfonate, a sulfated or sulfonated oxyalkylated alcohol        and a polyalkylene glycol alcohol ether;    -   U.S. Pat. No. 4,463,806 discloses a surfactant package        containing a water-soluble ether-linked sulfonate, an alcohol        and a petroleum sulfonate or alkylbenzene sulfonate;    -   U.S. Pat. No. 7,629,299 discloses the use of alcohol ether        sulfonates derived from unsaturated alcohol ethers;    -   US Pat. Publ. No. 2005/01999395 discloses the use of an alkali        and an alkylaryl sulfonate surfactant derived from alpha-olefins        for recovering oil from a formation;    -   US Pat. Publ. No. 2006/0185845 discloses a composition that        includes an aliphatic anionic surfactant and an aliphatic        nonionic additive for use in treating a formation;    -   US Pat. Publ. No. 2007/0191633 discloses a blend for recovering        oils that contains water or brine, an alcohol or alcohol ether        and a bifunctional anionic surfactant;    -   US Pat. Publ. No. 2009/0270281 discloses a surfactant mixture        including a hydrocarbon radical having 12-30 carbons and a        branched hydrocarbon having 6 to 11 carbon atoms for use in        tertiary oil extraction;    -   US Pat. Publ. No. 2011/0046024 discloses the use of an alkylated        hydroxyaromatic sulfonate, a solvent, a passivator and a polymer        for recovering oil from a formation;    -   US Pat. Publ. No. 2011/0048721 discloses the use of high        molecular weight sulfated internal olefin sulfonate sulfates and        high molecular weight dialkylphenol alkoxylate sulfonate        sulfates for use in oil recovery;    -   US Pat. Publ. No. 2011/0190174 discloses tristyrylphenol        alkoxylate sulfates and their use as a surfactant in oil        recovery applications;    -   US Pat. Publ. No. 2011/0281779 discloses the use of an anionic        ether surfactant comprising a branched hydrophobe group derived        from a Guerbet alcohol; and    -   US Pat. Publ. No. 2013/0068312 which discloses a nonionic        surfactant and a metal salt.

Despite the state of the art, there is a continuing need for newsurfactant packages and formulations useful in the recovery of fossilfluids, especially under high salinity and high temperature conditions.Provided herein are surfactant packages and surfactant formulationsaddressing the needs in the art and methods of using such formulations.

SUMMARY OF THE INVENTION

The present disclosure relates to a surfactant formulation for treatinga fossil fluid-bearing subterranean formation comprising a nonionicsurfactant, an organic acid selected from citric acid, diglycolic acid,glycolic acid and a salt thereof and injection water.

In a further embodiment, the present disclosure provides a process forpreparing a surfactant formulation for use in treating a fossilfluid-bearing subterranean formation by combining a nonionic surfactantwith an organic acid selected from citric acid, diglycolic acid,glycolic acid and a salt thereof and injection water.

In a still further embodiment, the present disclosure provides a processfor the recovery of fossil fluids from a subterranean formation byinjecting a surfactant formulation containing a nonionic surfactant, anorganic acid selected from citric acid, diglycolic acid, glycolic acidand a salt thereof and injection water into one or more injection wellslocated within the subterranean formation and recovering the fossilfluids from one or more producing wells. The injection well and theproducing well may be the same well or different wells.

In yet another embodiment, the present disclosure relates to asurfactant package for use in treating a fossil fluid-bearingsubterranean formation comprising a nonionic surfactant and an organicacid selected from citric acid, diglycolic acid, glycolic acid and asalt thereof.

DETAILED DESCRIPTION

If appearing herein, the term “comprising” and derivatives thereof arenot intended to exclude the presence of any additional component, stepor procedure, whether or not the same is disclosed herein. In order toavoid any doubt, all formulations claimed herein through use of the term“comprising” may include any additional additive, adjuvant, or compound,unless stated to the contrary. In contrast, the term, “consistingessentially of” if appearing herein, excludes from the scope of anysucceeding recitation any other component, step or procedure, exceptingthose that are not essential to operability and the term “consistingof”, if used, excludes any component, step or procedure not specificallydelineated or listed. The term “or”, unless stated otherwise, refers tothe listed members individually as well as in any combination.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e. to at least one) of the grammatical object of thearticle. By way of example, “a nonionic surfactant” means one nonionicsurfactant or more than one nonionic surfactant.

The phrases “in one embodiment,” “according to one embodiment,” and thelike generally mean the particular feature, structure, or characteristicfollowing the phrase is included in at least one embodiment of thepresent invention, and may be included in more than one embodiment ofthe present invention. Importantly, such phrases do not necessarilyrefer to the same embodiment.

If the specification states a component or feature “may”, “can”,“could”, or “might” be included or have a characteristic, thatparticular component or feature is not required to be included or havethe characteristic.

For methods of treating a fossil fluid-bearing subterranean formation,the term “treating” includes placing a chemical within the subterraneanformation using any suitable manner known in the art, for example,pumping, injecting, pouring, releasing, displacing, squeezing, spotting,or circulating the chemical into a well, well bore or subterraneanformation.

The term “fossil fluids” include oleaginous materials such as thosefound in oil field deposits, oil shales, tar sands, heavy oil deposits,and the like. The fossil fluids are generally a mixture of naturallyoccurring hydrocarbons that can be refined into diesel, gasoline,heating oil, jet oil, kerosene and other products called petrochemicals.Fossil fluids derived from subterranean formations may include, but arenot limited to, kerogen, bitumen, pyrobitumen, asphaltenes, oils orcombinations thereof.

The term “alkyl” is inclusive of both straight chain and branched chaingroups and of cyclic groups. Straight chain and branched chain groupsmay have up to 30 carbon atoms unless otherwise specified. Cyclic groupscan be monocyclic or polycyclic, and in some embodiments, can have from3 to 10 carbon atoms. The term “alkylene” is the divalent form of thealkyl groups defined above.

The term “aryl” includes carbocyclic aromatic rings or ring systems, forexample, having 1, 2 or 3 rings and optionally containing at least oneheteroatom (e.g. O, S or N) in the ring. Examples of aryl groups includephenyl, naphthyl, biphenyl, fluorenyl, furyl, thienyl, pyridyl,quionlinyl, isoquinlinyl, indoyl, isoindolyl, triazolyl, pyrrolyl,tetrazolyl, imidazolyl, pyrazolyl, oxazolyl, and thiazolyl.

The term “alkylaryl” refers to an aryl moiety to which an alkyl group isattached.

The term “alkylphenol” refers to a phenol moiety to which an alkyl groupis attached.

The term “alkali metal” refers to lithium, sodium or potassium.

The term “alkaline earth metal” refers to calcium, barium, magnesium orstrontium.

The term “lower carbon chain alcohols” refers to alcohols having no morethan 10 carbon atoms.

As used herein, a “surfactant” refers to a chemical compound that lowersthe interfacial tension between two liquids.

The term “nonionic surfactant” refers to a surfactant where themolecules forming the surfactant are uncharged.

As used herein, the term “substantially free” means, when used withreference to the substantial absence of a material in a formulation,that such a material is present, if at all, as an incidental impurity orby-product. In other words, the material does not affect the propertiesof the formulation.

The phrase “subterranean formation” encompasses both areas below exposedearth and areas below earth covered by water, such as an ocean or freshwater. Temperatures in a subterranean formation may range from about 25°F. to about 300° F. In some embodiments, the temperature of theformation is at least about 100° F., in other embodiments thetemperature of the formation is at least about 125° F., while in otherembodiments, temperature of the formation is at least about 150° F.

The present disclosure generally provides a surfactant formulation fortreating and recovering fossil fluids from a subterranean formation, andespecially for treating and recovering fossil fluids from a subterraneanformation under high salinity and/or high temperature conditions.According to one embodiment, the surfactant formulation includes anonionic surfactant, organic acid selected from citric acid, diglycolicacid, glycolic acid and a salt thereof and injection water. It has beensurprisingly found that the addition of minor amounts of the organicacid or salt thereof to the surfactant formulation adds salinity andhardness tolerance to the formulation, especially at high salinityconditions as well as phase stability at high temperature conditions.When the surfactant formulation is mixed with oil, ultra-low interfacialtensions are also observed. Moreover, additional components usuallyfound in surfactant formulations, such as carboxylated surfactants, thatare generally included to improve stability of the surfactantformulation, can be substantially reduced or eliminated thereby speedingup the process of developing an effective formulation as well asdecreasing the cost of the formulation. In one particular embodiment,the surfactant formulation is substantially free of carboxylatedsurfactants.

As noted above, the surfactant formulation includes a nonionicsurfactant. The nonionic surfactant can be any compound having ahydrophobic head, a hydrophilic tail and possible intermediate groups.In one embodiment, the nonionic surfactant comprises a compound having ahydrophobic head that is a natural or synthetically-based alkyl group oran alkylaryl group and a hydrophilic tail that is an alkoxylate group.The surfactant formulation can comprise one nonionic surfactant or amixture of nonionic surfactants.

According to one embodiment, the nonionic surfactant is an alkoxylatedalkylphenol or an alkoxylated alcohol. The alkoxylated alkylphenol oralkoxylated alcohol comprise one or more repeating C₁ to C₄ alkyleneoxide groups, preferably one or more ethoxylate groups, propoxylategroups or a mixture thereof. In some embodiments, the alkoxylatedalkylphenol or alkoxylated alcohol can comprise 2 to 50 alkylene oxideunits. According to other embodiments, the alkoxylated alkylphenol oralkoxylated alcohol can comprise 5 to 45 alkylene oxide units, while instill other embodiments, the alkoxylated alkylphenol or alkoxylatedalcohol can comprise 10 to 30 alkylene oxide units.

In another embodiment, the alkylphenol is phenol having one or morelinear or branched C₁ to C₂₅ alkyl groups attached, while in otherembodiments, the alkylphenol is phenol having one or more linear orbranched C₅ to C₂₀ alkyl groups attached, while in still furtherembodiments, the alkylphenol is phenol having one or more linear orbranched C₆ to C₁₄ alkyl groups attached. According to one particularembodiment, the alkylphenol is phenol having one or more p-octyl orp-nonyl groups attached.

According to another embodiment, the alcohol is a linear or branchedsaturated aliphatic alcohol compound comprising 5 to 30 carbon atoms. Instill other embodiments, the alcohol is a linear or branched saturatedaliphatic alcohol compound comprising 7 to 25 carbon atoms, while instill another embodiment, the alcohol is a saturated aliphatic alcoholcompound comprising 10 to 20 carbon atoms.

The alkoxylated alkylphenol or alkoxylated alcohols described above canbe produced using one of a number of different catalytic processes. Ofthese processes, one of the most common includes the use of an alkalinecatalyst such as sodium alkoxide, a quaternary ammonium base or sodiumhydroxide. At the end of the reaction, an acid (e.g., acetic acid,propionic acid, sulfuric acid, mixtures thereof) is used to neutralizethe alkaline catalyst, thereby producing a metal salt. Metal salt can besuspended in the nonionic surfactant produced in theses processes inconcentrations that range from about 500 to about 10000parts-per-million (ppm), where a value of about 1500 ppm is typical. Anexample of such a process can be found, among other places, in U.S. Pat.No. 2,677,700, which is incorporated herein by reference in itsentirety.

Other catalytic processes for producing the alkoxylated alkylphenol oralkoxylated alcohol include those that use a Lewis Acid catalysisprocess. An example of this process can be found in U.S. Pat. No.4,483,941, which is incorporated herein by reference in its entirety,and which describes the alkoxylation of organic materials in thepresence of at least one catalyst comprising BF₃ and metal alkyls ormetal alkoxides, SiF₄ and metal alkyls or metal alkoxides, and mixturesthereof. Other catalytic processes include the use of titaniumcatalysts, such as titanium isopropoxide and/or other titaniumtrialkoxide. These Lewis Acid catalysis processes, however, also must beneutralized with a base, thereby producing metal salts in concentrationsfrom about 500 to about 2500 parts-per-million (ppm). Also acidcatalyzed alkoxylations lead to harmful side products that must beremoved prior to use.

An additional catalytic process for preparing the alkoxylatedalkylphenol or alkoxylated alcohol can include the use of double metalcyanide (DMC) catalysts. DMC catalysts are known for epoxidepolymerization, i.e. for polymerizing alkylene oxides such as propyleneoxide and ethylene oxide to yield poly(alkylene oxide) polymers, alsoreferred to as polyether polyols. The catalysts are highly active, andgive polyether polyols that have low unsaturation compared with similarpolyols made using strong basic catalysts like potassium hydroxide. Inaddition to the preparation of polyether polyols, the catalysts can beused to make a variety of polymer products, including polyester polyolsand polyetherester polyols. The polyols can be used to preparepolyurethanes by reacting them with polyisocyanates under appropriateconditions.

As appreciated, DMC catalysts are not acidic or alkaline catalysts, butrather are transition metal catalysts which do not need to beneutralized as is the case with the acidic or alkaline catalysts. TheDMC catalysts are typically used at a concentration that is lower thanthe metal concentrations discussed herein for the acidic or alkalinecatalysts process, but are still present at a concentration of at least80 ppm. Because the DMC catalysts are not detrimental to the subsequentpreparation of polyurethanes they are allowed to remain with thepolyether polyol. Alternatively, removal of the DMC catalyst can beaccomplished with an alkali metal hydroxide to form an insoluble saltthat is then filtered.

According to another embodiment, the alkoxylated alcohol is analkoxylated Guerbet alcohol of formula (I)

R²—O—BO_(t)—PO_(u)—EO_(w)—H   (I)

wherein R² corresponds to an aliphatic, branched hydrocarbon groupC_(n)H_(2n+1) derived from a Guerbet alcohol where n corresponds to thenumber of carbon atoms and may range from 12 to 50; BO corresponds to abutoxy group; t corresponds to the number of butoxy groups present andmay range from 0 to 50; PO corresponds to a propoxy group; u correspondsto the number of propoxy groups present and may range from 0 to 50; EOcorresponds to an ethoxy group; and w corresponds to the number ofethoxy groups present and may range from 0 to 50 with the proviso thatt+u+w≧1.

Guerbet alcohols and methods of making them are well known to thoseskilled in the art. In the course of a Guerbet reaction, primaryalcohols are dimerized at high temperatures in the presence of acatalyst to primary alcohol products branched at the 2-position. Thereaction proceeds by the following sequential steps: (i) oxidation ofthe primary alcohol to an aldehyde; (ii) aldol condensation of thealdehyde; (iii) dehydration of the aldol product; and (iv) hydrogenationand reduction of the allylic aldehyde.

The Guerbet reaction may be carried out at a temperature range of aboutbetween 175° C.-275° C. Catalysts which may be used include NaOH, KOH,nickel, lead salts, oxides of copper, lead, zinc, chromium, molybdenum,tungsten and manganese, palladium compounds and silver compounds.

The Guerbet alcohol R²—OH is then alkoxylated in the next process step.The procedure for alkoxylation is known in principle to those skilled inthe art. It is likewise known to those skilled in the art that thereaction conditions can influence the molecular weight distribution ofthe alkoxylates.

In one embodiment, the alkoxylated Guerbet alcohol of formula (I) isprepared by base-catalyzed alkoxylation. The Guerbet alcohol is firstadmixed in a pressure reactor with alkali metal hydroxides, such aspotassium hydroxide, or with alkali metal alkoxides, such as sodiummethoxide. By means of reduced pressure, for example <100 mbar, and/oran increase in the temperature, for example from 30° C. to 150° C., itis possible to draw off water still present in the mixture. The alcoholis then present as the corresponding alkoxide. This is followed byinertization with inert gas and addition of the alkylene oxide attemperatures between 60° C.-180° C. and up to a pressure of max. 10 bar.At the end of the reaction, the catalyst can be neutralized by addingacid, such as acetic or phosphoric acid, and can be filtered off ifrequired.

In another embodiment, the alkoxylated Guerbet alcohol of formula (I)may be prepared by techniques known to those skilled in the art whichleads to narrower molecular weight distributions than in the case ofbase-catalyzed synthesis. To this end, the catalysts which may be usedare, for example, double hydroxide clays, double metal cyanidecatalysts, or Zn—Co type catalysts. To perform the reaction, the Guerbetalcohol is admixed with the catalyst and the mixture dewatered asdescribed above and reacted with the alkylene oxides as described above.Generally, not more than 250 ppm of catalyst based on the total weightof the mixture is used. The catalyst can remain in the final product dueto this small amount.

In yet another embodiment, the alkoxylated Guerbet alcohol of formula(I) may be prepared using a DMC catalyst or by acid-catalyzedalkoxylation. The acids may be Bronsted or Lewis acids. To perform thereaction, the Guerbet alcohol is admixed with the catalyst, and themixture dewatered as described above and reacted with alkylene oxides asdescribed above. At the end of the reaction, the acid can be neutralizedby adding a base, such as KOH or NaOH, and filtered off if required.

The block structure indicated in formula (I) may be obtained bysubsequently adding butlylene oxide, propylene oxide, and ethylene oxidein their respective amounts in any order to the Guerbet alcohol. Thus,in one embodiment, the Guerbet alcohol is first butoxylated with tbutlylene oxide units to form a butyloxated Guerbet alcohol, and thenpropoxylated with u propylene oxide units and then ethoxylated with wunits of ethylene oxide units. In some embodiments, different catalystsmay used during alkoxylation, for example, a DMC catalyst may be usedduring propoxylation while an alkali metal hydroxide may be used duringethoxylation. In other embodiments, the butylene oxide units, propyleneoxide units and ethylene oxide units are added to the Guerbet alcohol inrandom order. The properties of the resultant alkoxylated Guerbetalcohol can be tailored to enhanced oil recovery needs by the skilledartisan by selecting the number of BO, PO and EO units. The alkoxylatedGuerbet alcohol of formula (I) will comprise a terminal OH— group.

In one embodiment, the surfactant formulation comprises from about 0.005to about 10 weight percent of the nonionic surfactant, based on thetotal weight of the surfactant formulation. In another embodiment, thesurfactant formulation comprises from about 0.01 to about 5 weightpercent of the nonionic surfactant, based on the total weight of thesurfactant formulation. In still another embodiment, the surfactantformulation comprises from about 0.5 to about 3 weight percent of thenonionic surfactant, based on the total weight of the surfactantformulation.

The surfactant formulation further includes an organic acid selectedfrom citric acid, diglycolic acid, glycolic acid and a salt thereof. Ithas been surprisingly found that the surfactant formulation performsunexpectedly well in very fresh water to very hard, briney water (whereTDS can range from 1000 ppm to >200,000 ppm and hardness can range from0 ppm divalents to 30,000 ppm) when the organic acid or preferably asalt thereof is included in the surfactant formulation.

In some embodiments, the organic acid is selected from diglycolic acid,glycolic acid and a salt thereof. In yet another embodiment, the organicacid is diglycolic acid or a diglycolic acid salt. In still anotherembodiment, the organic acid is glycolic acid or a glycolic acid salt.

In one particular embodiment, the organic acid is provided as a powderin pure form which is then preferably used in an aqueous solution. Instill another embodiment, glycolic acid or glycolic acid salt may beproduced from sodium chloroacetate or chloroacetic acid under strongalkaline conditions. In still another embodiment, the organic acid isprovided in the form of a salt that can be illustrated by the alkalimetal or alkaline earth metal salts, such as sodium, calcium, lithium,magnesium, zinc and potassium, as well as the ammonium and alkanolaminesalts such as monoethanolamine and triethanolamine (which it is believedform alkanolammonium salts) salts, and the like and mixtures thereof. Inone particular embodiment, the organic acid is a glycolic acid salt, forexample, the sodium salt (i.e. sodium glycolate and/or disodiumglycolate).

The organic acid or salt thereof can be used in amounts sufficient toeffect surfactant formulation stabilization. These can be illustrated bysurfactant formulations containing ratios ranging between about 0.05parts by weight organic acid or a salt thereof to about 15 parts byweight nonionic surfactant to about 2 parts by weight organic acid or asalt thereof to about 10 parts by weight nonionic surfactant, while inother embodiments, the ratios may range between about 0.5 parts byweight organic acid or a salt thereof to about 12 parts by weightnonionic surfactant to about 1.25 parts by weight organic acid or a saltthereof to about 9 parts by weight nonionic surfactant.

The surfactant formulation also includes injection water. In oneembodiment, the injection water may be seawater, brine, fresh water froman aquifer, river or lake, or a mixture thereof. Thus, according to manyembodiments, the injection water contains minerals, for example, barium,calcium, magnesium, and/or mineral salts, for example, sodium chloride,potassium chloride, magnesium chloride.

It's well known water salinity and/or water hardness may affect recoveryof fossil fluids in a formation. As used herein, “salinity” refers tothe amount of dissolved solids in the injection water. Thus, in oneembodiment, the injection water has a salinity of at least about 20,000ppm. In another embodiment, the injection water has a salinity of atleast about 30,000 ppm. In still another embodiment, the injection waterhas a salinity of at least about 50,000 ppm. In still a furtherembodiment, the injection water has a salinity of at least about 100,000ppm. In a further embodiment, the injection water has a salinity of atleast about 200,000 ppm.

According to another embodiment, the surfactant formulation mayoptionally comprise a co-surfactant. In one embodiment, theco-surfactant is an alkylaryl sulfonate represented by the formula (II):

where R^(a) is hydrogen or an alkyl group containing from 1 to 3 carbonatoms, R^(b) is hydrogen or an alkyl group containing from 1 to 3 carbonatoms, R^(c) is an alkyl group having from 8 to 40 carbon atoms and A isa monovalent cation. In one embodiment, A is an alkali metal ion, anammonium ion or substituted ammonium ion. Examples of substitutedammonium ions include ammonium independently substituted with from 1 to4 aliphatic or aromatic hydrocarbyl groups having from 1 to 15 carbonatoms.

The compound of formula (II) may be obtained by the alkylation of anaromatic compound. In one embodiment, the aromatic compound is benzene,toluene, xylene or a mixture thereof. For embodiments where the aromaticcompound includes xylene, the xylene compound may be ortho-xylene,meta-xylene, para-xylene, or a mixture thereof.

The aromatic compound may be alkylated with a mixture of normal alphaolefins containing from C₈ to C₄₀, carbons and in some embodiment, C₁₄to C₃₀ carbons to yield an aromatic alkylate. The aromatic alkylate isthen sulfonated to form an alkylaromatic sulfonic acid which is thenneutralized with a source of alkali or alkaline earth metal or ammoniathereby producing an alkylaryl sulfonate compound. In one embodiment,the source is an alkali metal hydroxide, such as, but not limited to,sodium hydroxide or potassium hydroxide.

Other co-surfactants which may optionally be included in the surfactantformulation are the type derived from alkyl diphenyl oxide sulfonicacids and their salts. Examples include the monoalkyl diphenyl oxidedisulfonates, the monoalkyl diphenyl oxide monosulfonates, the dialkyldiphenyl oxide monosulfonates, and the dialkyl diphenyl oxidedisulfonates, and their mixtures.

For example, the surfactant formulation may optionally include aco-surfactant of the formula (III):

wherein R³ and R⁴ are, independently at each occurrence, hydrogen,linear or branched C₁-C₁₆ alkyl, or aryl; and X is independentlyhydrogen, sodium or potassium.

Co-surfactants of formula (III) contain a pair of sulfonate groups on adiphenyl oxide backbone. The two sulfonates provide double chargedensity to the molecule. The double charge provides a more powerful,more durable, and more versatile surfactant molecule when compared tosingle charge anionics. This higher local charge density results ingreater potential for solvating and coupling action. In addition, theflexible ether linkage of the molecule allows variable distance betweenthe sulfonates, allowing interactions with a broad variety of othermaterials in solution as well as excellent coupling with othersurfactants and ingredients.

In one embodiment, one or both of R₃ and R₄ are preferably independentlylinear or branched C₃-C₁₆ alkyl, preferably C₆-C₁₆ alkyl.

In one embodiment, X at each occurrence is preferably sodium.

Further preferred alkyl diphenyl oxide sulfonic acid basedco-surfactants include: disodium hexadecyldiphenyloxide disulfonate;disodium dihexadecyldiphenyloxide disulfonate; sodiumdipropyldiphenyleneoxide sulfonate, disodium didecyldiphenylene oxidedisulfonate, and disodium mono- and di-sec-hexyldiphenylene oxidedisulfonate, as well as their mixtures. Such materials can be readilyprepared by a person of ordinary skill in the art, using well knowntechniques. Suitable procedures are described in U.S. Pat. No.6,743,764, and references cited therein, which is incorporated herein byreference. Several of the foregoing materials are also commerciallyavailable under the DOWFAX™ brand (from The Dow Chemical Company).

In another embodiment, the co-surfactant is an internal olefinsulfonate. An internal olefin is an olefin whose double bond is locatedanywhere along the carbon chain except at a terminal carbon atom. Alinear internal olefin does not have any alkyl, aryl, or alicyclicbranching on any of the double bond carbon atoms or on any carbon atomsadjacent to the double bond carbon atoms. Typical commercial productsproduced by isomerization of alpha olefins are predominantly linear andcontain a low average number of branches per molecule.

Examples of commercially available internal olefin sulfonates, include,for instance, Petrostep™ S2, a C15-C18 IOS, is available from StepanCompany and Enordet™ internal olefin sulfonates available from ShellChemicals and other suppliers.

Internal olefin sulfonates may also be prepared by sulfonation of aC₆-C₂₀ internal olefin or mixture of internal olefins according towell-known methods. In one suitable approach, sulfonation is performedin a continuous thin-film reactor maintained at 10° C. to 50° C. Theinternal olefin or mixture is placed in the reactor along with sulfurtrioxide diluted with air. The molar ratio of internal olefin to sulfurtrioxide is maintained at a suitable ratio, e.g., from about 0.7:1 toabout 1.1:1. The sulfonated derivative of internal olefin or mixture maybe neutralized with alkali, e.g., sodium hydroxide, to form thecorresponding salt. The reaction is exothermic and the viscosity of thereaction product may depend on the amount of water present. Generalconditions and processes for sulfonation of olefins are disclosed inU.S. Pat. No. 4,252,192, the teachings of which are incorporated hereinby reference. The internal olefin used as a source for the C₆-C₂₀internal olefin sulfonate can be di-, tri-, or tetrasubstituted withlinear or branched alkyl groups. Internal olefin sources can be obtainedfrom a variety of processes, including olefin (e.g., ethylene,propylene, butylene) oligomerization, a-olefin metathesis,Fischer-Tropsch processes, catalytic dehydrogenation of long-chainparaffins, thermal cracking of hydrocarbon waxes, and dimerized vinylolefin processes. A well-known ethylene oligomerization process is theShell higher olefin process (SHOP), which combines ethyleneoligomerization to form a-olefins, isomerization of the a-olefins toform internal olefins, and metathesis of these internal olefins withbutenes or ethylene to form a-olefins of different chain lengths.Commercially available internal olefins made by SHOP typically containabout six mole percent or higher of tri-substituted internal olefins.Internal olefin sulfonates and their preparation are described in manyreferences, including U.S. Pat. Nos. 4,532,053, 4,555,351, 4,597,879,and 4,765,408, and U.S. Pat. Appl. Publ. No. 2010/0282467, the teachingsof which are incorporated by reference.

In one aspect, the internal olefin used to make the internal olefinsulfonate is produced by metathesis of an a-olefin and has a highproportion of disubstitution and a correspondingly low proportion oftrisubstitution. Such internal olefin sulfonates, which are disclosed inU.S. Pat. Appl. Publ. No. 2010/0282467, provide advantages for enhancedoil recovery, including lower optimal salinities.

According to one embodiment, the co-surfactant is added to thesurfactant formulation at a ratio of between about 1:20 parts by weightof co-surfactant to nonionic surfactant to about 1:1 parts by weight ofco-surfactant to nonionic surfactant. In another embodiment, theco-surfactant is added to the surfactant formulation at a ratio of about1:15 parts by weight of co-surfactant to nonionic surfactant to about1:5 parts by weight of co-surfactant to nonionic surfactant. In stillanother embodiment, the co-surfactant is added to the surfactantformulation at a ratio of about 1:12.5 parts by weight of co-surfactantto nonionic surfactant to about 1:7.5 parts by weight of co-surfactantto nonionic surfactant.

The surfactant formulation may further optionally include a dialkylsulfosuccinate represented by the formula (IV):

where R⁶ and R⁷ are each independently an alkyl group containing 5 to 13carbon atoms and M is an alkali metal ion, an alkaline earth metal ion,an ammonium ion or a substituted ammonium ion. Examples of substitutedammonium ions include ammonium independently substituted with from 1 to4 aliphatic or aromatic hydrocarbyl groups having from 1 to 15 carbonatoms.

According to one embodiment, R⁶ and R⁷ are independently a C₅ alkyl, aC₆ alkyl, a C₈ alkyl or a C₁₃ alkyl. These groups may be derived, forexample, from respectively, amyl alcohol, methyl amyl alcohol(1,4-dimethyl butyl alcohol), 2-ethyl hexanol, and mixed isomers ofalcohols.

In another embodiment, M is an alkali metal ion or alkaline earth metalion. In a further embodiment, M is sodium.

According to one embodiment, the dialkyl sulfosuccinate is added to thesurfactant formulation at a ratio of between about 1:15 parts by weightof dialkyl sulfosuccinate to nonionic surfactant to about 1:10 parts byweight of dialkyl sulfosuccinate to nonionic surfactant. In stillanother embodiment, the dialkyl sulfosuccinate is added to thesurfactant formulation at a ratio of between about 1:7.5 parts by weightof dialkyl sulfosuccinate to nonionic surfactant to about 1:5 parts byweight of dialkyl sulfosuccinate to nonionic surfactant. In a furtherembodiment, the dialkyl sulfosuccinate is added to the surfactantformulation at a ratio of between about 1:2.5 parts by weight of dialkylsulfosuccinate to nonionic surfactant to about 1:1 parts by weight ofdialkyl sulfosuccinate to nonionic surfactant.

In another embodiment, the surfactant formulation may optionally includea solvent. Examples of solvents include, but are not limited to,alcohols, such as lower carbon chain alcohols, for example, isopropylalcohol, ethanol, n-propyl alcohol, n-butyl alcohol, sec-butyl alcohol,n-amyl alcohol, sec-amyl alcohol, n-hexyl alcohol, and sec-hexylalcohol; lower carbon chain alcohols that have been alkoxylated withethylene oxide (EO), propylene oxide (PO) or butylene oxide (BO), forexample, n-butanol+1EO, n-butanol+2EO, n-butanol+3EO, n-hexanol+6EO,2-ethylhexanol+2EO and iso-butanol+3EO, alcohol ethers, polyalkylenealcohol ethers, such as ethylene glycol monobutyl ether, polyalkyleneglycols, such as ethylene glycol and propylene glycol, poly(oxyalkylene)glycols, such as diethylene glycol, poly(oxyalkylene) glycol ethers, orany mixtures thereof.

In one embodiment, the solvent is added to the surfactant formulation ata ratio of between about 20:1 parts by weight of solvent to nonionicsurfactant to about 1:1 parts by weight of solvent to nonionicsurfactant. In another embodiment, the solvent is added to thesurfactant formulation at a ratio of between about 15:1 parts by weightof solvent to nonionic surfactant to about 2.5:1 parts by weight ofsolvent to nonionic surfactant. In still another embodiment, the solventis added to the surfactant formulation at a ratio of between about 10:1parts by weight of solvent to nonionic surfactant to about 5:1 parts byweight of solvent to nonionic surfactant.

In yet another embodiment, the surfactant formulation may optionallyinclude a chelant, or a polymer.

Examples of chelants which may be used include, but are not limited to,EDTA, EDTA salts, EDDS, EDDS salts, phosphate compounds, ascorbic acid,tetrasodium iminodisuccinate, citric acid, dicarboxymethylglutamic acid,maleic acid, diethylenetriaminepentacetic acid, cyclohexantrans-1,2-diaminetetraacetic acid, ethanoldiglycine, diethanolglycine,hydroxyethyl-ethylene-diaminetriacetic acid, ethylene bis[2-(o-hydroxyphenyl)-glycine], nitrilotriacetic acid (NTA), a nonpolaramino acid, methionine, oxalic acid, a polar amino acid, arginine,asparagine, aspartic acid, glutamic acid, glutamine, lysine, ornithine,a siderophore, desferrioxamine B, hydrolysed wool, succinic acid, sodiummetaborate, sodium silicate, sodium orthosilicate, and any mixturethereof.

In one particular embodiment, the surfactant formulation issubstantially free of EDTA, EDTA salts and phosphate compounds.

According to another embodiment, the surfactant formulation comprisesfrom about 0 to about 10 weight percent of chelant, based on the totalweight of the surfactant formulation. In another embodiment, thesurfactant formulation comprises from about 0.01 to about 5 weightpercent of chelant, based on the total weight of the surfactantformulation. In yet another embodiment, the surfactant formulationcomprises from about 0.1 to about 3 weight percent of chelant, based onthe total weight of the surfactant formulation.

Examples of polymers include, but are not limited to, polyacrylamides,partially hydrolyzed polyacrylamide, polyacrylates, ethyleniccopolymers, biopolymers, carboxymethylcellulose, polyvinyl alcohols,polystyrene sulfonates, polyvinylpyrrolidone, AMPS(2-acrylamide-2-methyl propane sulfonates), modified starches andmixtures thereof. Examples of ethylenic copolymers include copolymers ofacrylic acid and acrylamide, acrylic acid and lauryl acetylate, laurylacrylate and acrylamide. Examples of biopolymers include xanthan gum andguar gum.

In one embodiment, the surfactant formulation comprises from about 0 toabout 2 weight percent of polymer, based on the total weight of thesurfactant formulation. In another embodiment, the surfactantformulation comprises from about 0.01 to about 1 weight percent ofpolymer, based on the total weight of the surfactant formulation. Instill another embodiment, the surfactant formulation comprises fromabout 0.2 to about 0.5 weight percent of polymer, based on the totalweight of the surfactant formulation.

In still another embodiment, the surfactant formulation may optionallyinclude an alkali metal hydroxide, carbonate or chloride. The additionof such materials can: alter the surface properties of the formation sothat surfactant retention is reduced; provide stability to ethersulfates from hydrolysis; activate surfactants in the crude oil; andraise the salinity of the injection water so a salinity gradient isachieved as the formulation propagates through the formation. In oneembodiment, the alkali metal hydroxide, carbonate or chloride is addedto the surfactant formulation prior to being pumped into the fossilfluid-bearing subterranean formation. In another embodiment, thesurfactant formulation contains from about 0.01 weight percent to about2 weight percent, for e.g., from about 0.05 weight percent to about 1.5weight percent or from about 0.01 weight percent to about 1 weightpercent, of alkali metal hydroxide, carbonate or chloride based on thetotal weight of the surfactant formulation.

The surfactant formulation may be prepared by a process of mixing thenonionic surfactant with an organic acid selected from citric acid,diglycolic acid, glycolic acid, and a salt thereof and injection water.The components may be mixed together in any order using customarydevices, such as, but not limited to, a stirred vessel or static mixer.

In another embodiment, there is provided a method for designing asurfactant formulation for use in recovering fossil fluids from asubterranean formation. The method includes measuring the temperature ofthe subterranean formation, measuring the interfacial tension in theinjection water and fossil fluid, adding a nonionic surfactant to theinjection water to decrease the interfacial tension in the injectionwater and fossil fluid to less than 1×10⁻¹ dynes/cm, and adding anorganic acid selected from citric acid, diglycolic acid, glycolic acidand a salt thereof to the mixture of injection water and nonionicsurfactant in an amount necessary to make the mixture phase stable atthe temperature of the subterranean formation. In one embodiment, theinjection water has a salinity of at least about 20,000 ppm and thesubterranean formation is at a temperature in the range between about80° F. to about 300° F., while in other embodiments the formation is ata temperature in the range between about 125° F. to about 300° F.

In another embodiment, there is provided a surfactant package fortreating a fossil fluid-bearing subterranean formation comprising anonionic surfactant, an organic acid selected from citric acid,diglycolic acid, glycolic acid and a salt thereof and injection water.In a further embodiment, the surfactant package comprises an alkoxylatedalkylphenol, alkoxylated alcohol or alkoxylated Guerbet alcohol offormula (I) described above and glycolic acid or a salt thereof. In someembodiments, the surfactant package can be further combined withinjection water and optional components described above to form asurfactant formulation.

The surfactant formulation described herein may be injected into one ormore injection wells located within the subterranean formation such thatfossil fluid is subsequently produced from one or more producing wells.In one embodiment, the injection well and producing well are the samewell. In another embodiment, the injection well and producing well areadjacent to one another. In one embodiment, the subterranean formationtemperature conditions are between about 80° F. and about 300° F.,preferably between about 125° F. and about 300° F.

Consideration must be given to the fact that although this disclosurehas been described and disclosed in relation to certain preferredembodiments, obvious equivalent modifications and alterations thereofwill become apparent to one of ordinary skill in this art upon readingand understanding this specification and the claims appended hereto. Thepresent disclosure includes the subject matter defined by anycombination of any one of the various claims appended hereto with anyone or more of the remaining claims, including the incorporation of thefeatures and/or limitations of any dependent claim, singly or incombination with features and/or limitations of any one or more of theother dependent claims, with features and/or limitations of any one ormore of the independent claims, with the remaining dependent claims intheir original text being read and applied to any independent claim somodified. This also includes combination of the features and/orlimitations of one or more of the independent claims with the featuresand/or limitations of another independent claim to arrive at a modifiedindependent claim, with the remaining dependent claims in their originaltext being read and applied to any independent claim so modified.Accordingly, the presently disclosed invention is intended to cover allsuch modifications and alterations, and is limited only by the scope ofthe claims which follow, in view of the foregoing and other contents ofthis specification.

What is claimed is:
 1. A surfactant formulation for treating a fossilfluid-bearing subterranean formation comprising a nonionic surfactant,organic acid selected from citric acid, diglycolic acid, glycolic acidand a salt thereof, and injection water.
 2. The surfactant formulationaccording to claim 1, wherein the nonionic surfactant comprises acompound having a hydrophobic head that is a natural orsynthetically-based alkyl group or an alkylaryl group and a hydrophilictail that is an alkoxylate group.
 3. The surfactant formulationaccording to claim 1, wherein the nonionic surfactant is an alkoxylatedalkylphenol or an alkoxylated alcohol comprising one or more repeatingC₁ to C₄ alkylene oxide groups.
 4. The surfactant formulation accordingto claim 1, wherein the nonionic surfactant is an alkoxylatedalkylphenol having one or more linear or branched C₁ to C₂₅ alkyl groupsattached.
 5. The surfactant formulation according to claim 1, whereinthe nonionic surfactant is an alkoxylated linear or branched saturatedaliphatic alcohol compound comprising 5 to 30 carbon atoms.
 6. Thesurfactant formulation according to claim 1, wherein the nonionicsurfactant is a an alkoxylated Guerbet alcohol of formula (I)R²—O—BO_(t)—PO_(u)—EO_(w)—H   (I) wherein R² corresponds to analiphatic, branched hydrocarbon group C_(n)H_(2n+1) derived from aGuerbet alcohol where n corresponds to the number of carbon atoms andmay range from 12 to 36; BO corresponds to a butoxy group; t correspondsto the number of butoxy groups present and may range from 0 to 50; POcorresponds to a propoxy group; u corresponds to the number of propoxygroups present and may range from 0 to 50; EO corresponds to an ethoxygroup; and w corresponds to the number of ethoxy groups present and mayrange from 0 to 50 with the proviso that t+u+w≧1.
 7. The surfactantformulation according to claim 1, wherein the organic acid is glycolicacid or a glycolic acid salt.
 8. The surfactant formulation according toclaim 7, wherein the glycolic acid salt is sodium glycolate and/ordisodium glycolate.
 9. The surfactant formulation according to claim 1,wherein the injection water is seawater, brine, fresh water from anaquifer, river or lake, or a mixture thereof.
 10. A method of preparinga surfactant formulation for treating a fossil fluid-bearingsubterranean formation comprising mixing a nonionic surfactant with anorganic acid selected from citric acid, diglycolic acid, glycolic acidand a salt thereof and injection water.
 11. A process for recoveringfossil fluids from a fossil fluid-bearing subterranean formationcomprising injecting the surfactant formulation of claim 1 into one ormore injection wells such that oil is subsequently produced from one ormore producing wells.
 12. A surfactant package for treating a fossilfluid-bearing subterranean formation comprising a nonionic surfactantand an organic acid selected from citric acid, diglycolic acid, glycolicacid and a salt thereof.
 13. The surfactant package according to claim12, wherein the nonionic surfactant is an alkoxylated alkylphenol havingone or more linear or branched C₁ to C₂₅ alkyl groups attached.
 14. Thesurfactant formulation according to claim 12, wherein the nonionicsurfactant is an alkoxylated linear or branched saturated aliphaticalcohol compound comprising 5 to 30 carbon atoms.
 15. The surfactantformulation according to claim 12, wherein the nonionic surfactant is aan alkoxylated Guerbet alcohol of formula (I)R²—O—BO_(t)—PO_(u)—EO_(w)—H   (I) wherein R² corresponds to analiphatic, branched hydrocarbon group C_(n)H_(2n+1) derived from aGuerbet alcohol where n corresponds to the number of carbon atoms andmay range from 12 to 36; BO corresponds to a butoxy group; t correspondsto the number of butoxy groups present and may range from 0 to 50; POcorresponds to a propoxy group; u corresponds to the number of propoxygroups present and may range from 0 to 50; EO corresponds to an ethoxygroup; and w corresponds to the number of ethoxy groups present and mayrange from 0 to 50 with the proviso that t+u+w≧1.
 16. The surfactantformulation according to claim 12, wherein the organic acid is glycolicacid or a glycolic acid salt.